The present invention relates to glass plates each having thereon a water-repellent film. Such water-repellent glass plates can be used for various industrial uses (e.g., mirror), architectural windows, automotive windows, watercraft windows, and aircraft windows. The water-repellent film is required to have good weather resistance, good abrasion resistance, good scratch resistance, and good durability, as well as good water-repellency, for a long time. The water-repellent film is further required to have no defects such as cracks. The water-repellent film is still further required to be formed on a glass substrate in an easy, effective manner.
Hitherto, various water-repellent glass plates (panes) have been proposed. For example, Japanese Patent Unexamined Publication JP-A-60-231442 discloses a water-repellent film formed on a glass substrate. This film is made of a mixture of a first polymer for enhancing the attachment of the film to the glass substrate and a second polymer for imparting water repellency to the film. The proportion of the first polymer in the film gradually decrease from the glass substrate surface toward the outer surface of the film, and in contrast that of the second polymer therein gradually increase. The water-repellent film is formed thereon, for example, by plasma polymerization method. In this publication, the temperature of the glass substrate during the formation of the water-repellent film is not disclosed nor suggested at all.
JP-A-3-205327 discloses a method for producing a water-repellent glass plate. This method comprises a first step of applying a polysiloxane compound to a glass substrate and a second step of attaching the polysiloxane compound to the surface of the glass substrate by corona discharge or ultraviolet irradiation. The polysiloxane compound contains at least one group selected from --OR, --NH.sub.2, --ON.dbd.C--R.sub.2, and --O--COR where R is hydrogen or an alkyl group having a carbon atom number of from 1 to 4. In this publication, the temperature of the glass substrate during the first step is not specified at all.
JP-A-5-51238 discloses a water-repellent glass plate having a glass substrate and a water-repellent layer formed thereon. The water-repellent layer has a metal oxide phase and water-repellent fine particles (e.g., PTFE and BN) dispersed in the metal oxide phase. In this publication, the temperature of the glass substrate during the application of a coating liquid for forming the water-repellent layer is not specified at all.
JP-A-6-279062 discloses a water-repellent glass plate having a glass substrate, a silicon oxide coating layer formed on the glass substrate, and a water-repellent layer formed on the coating layer. The water-repellent layer is prepared by vacuum CVD method and is made of a fluorosilicone which is represented by the formula of CF.sub.3 (CF.sub.2).sub.p (CH.sub.2).sub.m SiX.sub.n (CH.sub.3).sub.3-n where X is chlorine, 5.ltoreq.p.ltoreq.15, m=2, and 1.ltoreq.n.ltoreq.3. This fluorosilicone has at least one chlorine at its one end. It is preferable that the fluorosilicone layer of this publication is attached thereto by vacuum CVD method, while the glass substrate is heated, in order to accelerate its reaction with the surface of the glass substrate. It is stated in this publication that the heating temperature of the glass substrate varies depending on the kinds of the material of the glass substrate surface and on the kinds of water-repellent agent, and that a heating temperature of from 40 to 100.degree. C. (e.g., about 80.degree. C.) will suffice.
There is a demand for a water-repellent glass plate that has superior abrasion resistance for a long time.